1. Field of the Invention
This invention relates to speakerphones useful in teleconferencing applications.
2. Brief Description of the Related Art
Speakerphones are often used in a conference room setting, with conference call participants seated around a table, and generally include at least one speaker and at least one microphone. Speakerphone units are generally configured with the speaker(s) oriented to provide adequate sound quality in a 360.degree. range, so that the sound quality perceived by conference call participants is not diminished at certain locations in the room or around the conference table. Likewise, the microphone(s) are oriented to provide 360.degree. sound pick-up, so that any differences in signal level and quality as participants speak from different parts of the room or at different locations around a conference table are minimized.
One configuration that has previously been used in an attempt to achieve these goals includes a speaker and a microphone co-axially aligned with a vertical axis of the speakerphone unit. In this configuration, the microphone and the speaker are oriented in opposite directions, i.e., the microphone upwards and the speaker downwards or vice versa. U.S. Pat. No. 3,069,508 shows a telephone instrument having a top-mounted, upward-oriented microphone and a downward-oriented speaker mounted on the bottom of the speakerphone unit. Sound output from the speaker exits the housing through apertures in the sides of the unit. Likewise, a second set of apertures in the housing allow for passage of sound waves into the housing to the microphone. An insulating disc separates the speaker from the microphone to prevent the direct transmission of sound waves from the speaker to the microphone.
Prior art units with this configuration have an upright profile, to the extent that the sight-lines of the participants around the conference table may be blocked by the speakerphone unit, to the distraction of the conference call participants. Additionally, prior art speakerphones with a downward-oriented microphone mounted on the lower side of the speakerphone unit are known. For example, U.S. Pat. No. 4,078,155 shows a speakerphone having a cylindrical housing and including a downward-oriented, omni-directional microphone mounted at the apex of an inverted conical section, the sloped surface of which rises at a 30.degree. angle from the horizontal. The conical section is surrounded by a large cavity, encircling the microphone, that rises vertically for some distance. A diaphragm separates the speaker from the microphone. U.S. Pat. No. 4,831,656 shows a similar structure, with a microphone mounted at the apex of a 22.degree. cone.
A readily apparent disadvantage of this design is that the open cavity surrounding the microphone extends vertically for some distance, in turn causing the entire unit to be tall and obtrusive. As discussed above, speakerphones having a tall unit profile are obtrusive and distracting to conference call participants. It would, therefore, be desirable to have an improved speakerphone.